The present invention relates to an image outputting system, an image outputting method for creating a color proof of a halftone image for checking the final form of the printed matter beforehand or for creating the final product using an electro-photographic image outputting apparatus. The present invention also relates to the image outputting method, a program for executing the foregoing method and a computer-readable information recording medium on which the program is recorded.
In recent years, DTP (Desk Top Publishing) and the like have been becoming more popular, and as a result image editing and page adding operations using a computer are becoming standard, and full digital editing is no longer rare.
In these types of processes, image setter output in which image data which has been subjected to page editing is directly output to film, or CTP (computer to plate) output in which image recording is performed directly on the printing plate and CTC (computer to cylinder) output in which image recording is performed directly on the printing plate which is wound onto the cylinder of the printer are being performed with the object of improving efficiency.
Furthermore, proofs are created and used in 3 main applications in the correction processes in these types of printing processes, and these are (1) error checking at the operation site, or in other words, internal correction; (2) external correction which is submitted for checking of the completed work by the designer or the order holder; (3) print sample that is submitted to the person in charge of printing as a sample of final print material. The final form of the printed material was checked beforehand to determine if there are errors in the document layout, in color, or in text.
In this system, there was the problem that some film output and printing plate output must be performed just for proof checking, and when proofing is done using print proofs and other proof material, film and printing plates are wasted and many unnecessary operations had to be performed.
As a result, in the process of performing full digital image creation and editing using a computer in particular, there is demand for systems which performs direct-color image output called DDCP (Direct Digital Color Proof) or DCP (Digital Color Proof). Prior to recording from the digital image data processed on the computer onto the plate making film using an image setter or the like, or performing final printing operations for creating a direct printing plate using CTP, or performing direct image recording on the printing plate that is wound on the cylinder of the printer using CTC, a color proof which reproduces output showing the digital image that was processed by the computer is created, and the picture pattern, tone and the text and the like were checked.
Another example of a device for creating a color proof is a color proof creation device in which light spots composing plural lights having combinations of different wavelengths such as R, G and B are exposed on a silver salt color light-sensitive material based on halftone dot image data for each of the color separated halftone dot originals, and halftone dot images are reproduced and a color proof is created by performing color development for dots of each of the 3 fundamental colors Y, M and C.
Meanwhile, there is a comprehensive layout (abbreviated and referred to as comp hereinafter), which does not require the image quality of a color proof, but shows overall design and is used for obtaining approval from an advertiser for example. In the past, a color laser printer using an electro-photographic system was used for creating this comp.
However, with the increase in quality of the color laser printer in recent years, high speed and high grade color output has become possible at a low cost and as a result, there is increasing demand for not only comp applications, but also DCCP applications. That is to say there is increasing demand for use of color laser printers in creating color proofs, as well increased demand for the output from the color laser printer to be used as final product.
For the outputted product of a color laser printer, halftone-dot images are formed and output by forming halftone-dots of areas including a plurality of pixels, in order to simultaneously achieve a number of lines and gradation expression close to that of the technology existing heretofore. Also, in the case of a multi-value dot image formed of pixels with multiple values, there are ways to suppress deterioration of image gradation caused by instability in the formation of the intermediate tone pixels due to the process called electro-photography. These include limiting the number of intermediate tone pixels in the area forming one pixel (See Patent Document 1 for example) and changing the number of intermediate tone pixels in the area forming one halftone-dot using density values (See Patent Document 2 for example).                [Patent Document 1]                    Tokkaisho 61-189774 (Japanese Non-Examined Patent Publication)                        [Patent Document 2]                    Tokkai 2000-350024 (Japanese Non-Examined Patent Publication)                        
However, because in general, the resolution is lower in the color laser printer than the conventional printing system such as the offset printer, the outline portion of each object in the image is not necessarily shaped as a complete halftone-dot and in some cases portions may be missing. In addition, in the case of the multi-value halftone-dot image in which the pixel is formed with multiple values, the halftone-dot including an intermediate gradation pixel with a portion missing is extremely weak due to instability in the formation of the intermediate gradation pixels. Consequently, smoothness of the outline of the intermediate tone objects of intermediate gradation density in particular is lost and this gives the impression that the outline which was originally linear has a saw tooth shape.
This type of deterioration in image quality did not cause problems for comp application, but it poses a problem with regards to color proof application and use as final product.